It's not my intention to cast aspersions on what he found. The GSS, however, offers an alternative finding. The following table shows the average IQ as estimated from mean wordsum results converted to IQ scores assuming a white average of 100 and a standard deviation of 15 by wealth category. To allow wealth formation to have occurred and to avoid racial confounding, results are restricted to non-Hispanic whites aged 35-70 years old (n = 824):
|Less than $100k||98.2|
The differences aren't huge but they clearly exist. The correlation between wordsum scores and income in the GSS is 50% stronger than it is between wordsum scores and wealth (r-values of .27 and .18, respectively), a result I admittedly found surprising. I'd assumed that if anything wealth would correlate more strongly with income, the lottery winner who is broke a decade later or the former NBA player who is similarly so a decade after his career ends as salient examples of why.
On the other hand, a lot of wealth comes from inheritance. Income is primarily a function of an individual's capabilities while wealth is more a function of the capabilities of his family.
The consequences of regression to the mean are blunted in the case of wealth but not so much in the case of income. A sharp guy with modest parents may earn a lot but having not started with much--while also shouldering a financial burden on behalf of his family--never accumulates that many assets. And the modest son with rich parents may not be able to command much of a salary, but affluence will still roll downhill to him.
GSS variables used: BORN(1), RACECEN1(1), WEALTH(1-5,6-8,9,10-15), AGE(35-70), CONINC